It is well known that if two thin strips of metal having different thermal coefficients of expansion are laminated together, they will bend and straighten in a manner dependent on the temperature. This movement is because changes in temperature cause one strip to lengthen more than the other. Since both strips are bonded together, the only way this length difference can be accommodated is by curling. The standard equation for the bending of a bimetallic strip is:D=K(DT)(De)L2/t   (Eq. 1)
where D is the distance the strip bends measured at the end of the strip, (DT) is the temperature difference relative to the temperature when the two layers were bonded, (De) is the thermal expansion difference, L is the length of the strip, t is the thickness, and K is a constant. Bimetallic strips are useful as thermometers and oven safety locks.